没有外部验证器或type（）的Python 3 isinstance bool？

Question

so I'm trying to pass through a list and identify the different int, float, and bool. Now I'm aware after research from stack here that bool is a subclass of int as per the initial Python versions and that I need some special handling to identify bool from int like so:

listone = ['232.54',False,'656',27.3,'5',' ',True,'-434','76.67','8.45','s',23]

for i in listone:
if isinstance(i,int):
    print(i,'INT')
elif isinstance(i,float):
    print(i,'FLOAT')
elif isinstance(i,str):
    print(i,'STR')

elif isinstance(i,bool):
    #SPECIAL HANDLING 
    print(i,'BOOL')

However even after doing so I still get the printout:

232.54 STR
False INT
656 STR
27.3 FLOAT
5 STR
STR
True INT
-434 STR
76.67 STR
8.45 STR
s STR
23 INT

Now, is there any way that I can get this printed out with some special handling, without using external validator like this or by using "type() == "? Thanks

Answer 1

You're on the right track to observe that bool is a subclass of int . The issue is the behavior of isinstance . From the documentation (emphasis added):

isinstance ( object, classinfo )

Return true if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof . If object is not an object of the given type, the function always returns false. If classinfo is a tuple of type objects (or recursively, other such tuples), return true if object is an instance of any of the types. If classinfo is not a type or tuple of types and such tuples, a TypeError exception is raised.

Since bool is a subclass of int , any bools passed into your if/elif clauses will not make it past the first if statement, isinstance(<bool>, int) will return True . You need to put the check for bool before the check for int .

Answer 2

Just change the order of your checks to check for bool first. That way it won't get caught by your check for int .

listone = ['232.54',False,'656',27.3,'5',' ',True,'-434','76.67','8.45','s',23]

for i in listone:

    if isinstance(i, bool):
        #SPECIAL HANDLING 
        print(i, 'BOOL')
    elif isinstance(i, int):
        print(i, 'INT')
    elif isinstance(i, float):
        print(i, 'FLOAT')
    elif isinstance(i, str):
        print(i, 'STR')